HELICAL RETAINING WALL REPAIRSPROJECT INFORMATION
Kensington Golf and Country Club, of Naples, Florida is situated within close proximity to the spectacular beaches and clear waters of the Gulf Of Mexico. This gated golf community has a total of 565 homes and condominium units. There are four neighborhoods of coach homes and six neighborhoods of single-family homes located on the golf course and all have fantastic lake front views.
PROJECT CHALLENGES
The aging timber piers and wood bulkhead protecting the lakefront property owner’s homes slowly came apart after twenty-five (25) years of existence. The existing tie-backs consisted of a half inch ½” galvanized cable which had corroded away over the years. The tie-backs holding the wood wall in alignment were failing causing sections of the wood bulkhead to fail and collapse into the lake. After struggling with rotting wooden lake walls, the board at Kensington Golf and Country Club elected to replace the crumbling structure at a reasonable cost.
The project was put out to bid to construct a new state of the art vinyl seawall with helical tieback anchors. Florida Marine Construction was selected as the most qualified contractor to undertake replacement of two thousand eight-hundred (2,800) feet of new vinyl seawall. The project entailed drilling of rock to install wood marine pilings with a minimum of four (4) foot embedment into rock strata.
The Naples geographic location has significant sub-surface rock with densities reaching 160 P.S.I. per cubic foot. The marine contractor realized the complexity of the project would require an experienced foundation piling expert. Coastal Foundation Solutions was contracted by Florida Marine Construction to provide drilling services and helical anchor tie-back installation for the project.
HELICAL TIEBACK INSTALLATIONTHE SOLUTION
Our highly experienced engineering team assisted us with a comprehensive helical tie-back anchor strategy and cost savings design to help minimize disruption of waterfront home-sites and landscaping. Coastal Foundation Solutions having many years of experience in the fields of marine construction and foundation piling, have profound knowledge and insights into the most advanced and effective helical and drilling equipment available. We are proficient at installing permanent and durable helical piles across Florida, at a competitively low cost.
ROCK DRILLING SERVICES
Coastal Foundation Solutions mobilized their sixty (60) foot modular barge into Kensington Golf and Country Club to drill 511 holes through hard lime rock. The rock varied in thickness from a couple of foot to five foot in thickness. Consequently, the pilings achieved approximately 4 to 8 foot of penetration into the rock substrate. We utilized a 25 ton excavator with a mast drill and “Down the Hole Hammer” to penetrate the rock. On average, we were drilling through rock at the rate of 15-20 minutes. The diameter of the holes we were requested to drill were 38” in circumference. The project was completed ahead of the projected schedule.
HELICAL ANCHOR INSTALLATION
A compact modular aluminum barge was utilized to perform helical installation construction at Kensington Golf and Country Club. The helical anchors were driven into the sub-strata using a 7,000# mini excavator with dual hydraulic output functions. A Helical Anchoring System confirmed to be ideally appropriate for this wood bulkhead renovation application. A single row of galvanized Seawall Savers Anchors were installed using a hydraulically powered 6,000# Eskridge Hydraulic Anchor drive head and were rotated into the soil until the essential installation torques were secured thus confirming their capacity. These anchors were all successfully installed and load tested to provide ultimate capacities up to 13,000 lbs.
EQUIPMENT MOBILIZATION
Coastal Foundation Solutions elected to incorporate a combination of modular floating equipment including:
60-foot steel barge with a 25-ton excavator to provide rock drilling services for the bulkhead project. We deployed our “Down the Hole Hammer” to drill through rock strata.
A 26-foot aluminum utility barge with a 3.5-ton excavator with custom rigging for an Eskridge 6k hydraulic rotary torque drive unit to install helical tie-back anchors. Enough materials were loaded onto the aluminum barge to accommodate for 10 helical pile anchors installations.
We utilized a 24-foot crew boat to mobilize and push our modular barges around the project location. The tiebacks would be installed prior to the construction of the wall, then embedded within the wall.
PRODUCTS
The Seawall Saver helical tieback anchors would be installed prior to the construction of the new vinyl seawall. Then embedded within the marine piling with a 1” galvanized all thread and 4” x 4” epoxy coated washer plate and nut. A subsurface soil investigation revealed that the planned retaining wall tiebacks would bear in medium dense sand.
Square shaft 1 ½” helical tiebacks were selected to provide the lateral support system for the wall. CHS selected 10”-12” lead sections and were installed to lengths ranging from 17 to 28 feet from the wall facing.
One continuous row of Seawall Saver helical anchor tiebacks were proposed with lateral positioning of about five (5) feet and the terminal connection to the wall at about 2 feet below the top of wall.
The helical tiebacks were designed for a downward installation angle of 15 to 22 degrees and a (horizontal) design working tension load of 13 kips.
Five-hundred and eleven (511) hot dipped galvanized Seawall Saver 10”-12” square shaft helical lead sections were installed on five (5) foot centers.
One thousand twenty-two seven (7) foot square shaft lead sections were implemented to grasp final design torque capacities.
Each individual helical anchor was load tested with a 30-ton hydraulic jack to insure required load capacity of 13 Kips. In addition, this methodology provides zero slippage of installed helical anchor.
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